JPH1157612A - Method for corrosion-preventive surface treatment, steel product with corrosion-preventive surface treatment applied and its use method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating a surface to be corrosion-resistant by which it is possible to manufacture a steel material which can be used even in an environment in which chloride is airborne on a coastal zone and a steel material treated with a corrosion-resistant surface ant its usage. SOLUTION: This method for treating the surface to be corrosion-resistant is to apply a resin coat containing 0.1-15 mass % of chromium sulfate 10-40 mass % of butyral resin or a resin comprising a mixture of the butyral resin and a resin which is compatible with the butyral resin as main components, for the solid content of the resin coat, to the surface of a steel material. The effects of inhibiting the penetration of C1 of a rusty layer further increase when one or more different types selected from among the oxyacid ions of PO4 <3-> , MoO4 <2-> , WO4 <2-> , VO3 <-> and NO3 <-> are contained in the resin coat. In addition, the steel material treated with a corrosion-resistant surface (including chromium steel with high pitting-resistance) has the resin coat applied by the method. The usage of this steel material includes use applications for concrete forming and underground laying structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion surface treatment method for a steel material, and more particularly, to an anticorrosion surface treatment method for suppressing corrosion by forming a dense protective rust layer on the surface of a steel material. The present invention relates to a corrosion-resistant surface-treated steel material subjected to the treatment and a method of using the same.

[0002]

2. Description of the Related Art Steel materials are widely used in various fields of industry, steel types corresponding to the respective applications have been developed, and appropriate anticorrosion measures have been taken.

[0003] Steel materials used for civil engineering, building structures and the like are also improved in corrosion resistance in terms of material, while various surface treatments are taken to prevent or suppress corrosion. However, this is not always sufficient, and particularly in an environment where a large amount of chlorides fly, corrosion is accelerated, and depending on the type of steel, corrosion occurs in a pit-like manner.

[0004] For example, steel materials used in concrete, such as reinforcing bars and steel frames of concrete structures, are usually hardly corroded because their surfaces are covered with concrete. However, in coastal areas and areas where deicing agents such as rock salt are sprayed, chloride particles adhere to the concrete surface, and chloride ions (Cl ⁻ ) become water (H ₂ O),
The oxygen diffuses and penetrates into the concrete together with oxygen (O ₂ ) to reach the surface of a steel material such as a reinforcing steel, and when the Cl ⁻ concentration in that portion exceeds a certain critical concentration, it corrodes. Therefore, the corrosion protection of steel in concrete in the environment in which such chlorides are flying, Cl ^- measures it is necessary for corrosion.

Conventionally, as a countermeasure against corrosion of a steel material used in concrete, for example, a heavy-corrosion-proof type epoxy reinforcing bar in which a reinforcing bar is coated with an epoxy resin is known. In this method, corrosion is prevented by shielding a reinforcing bar from a corrosive environment with an epoxy resin having a thickness of several hundred μm, but it is not widely used because of high cost.

In addition, Cu and W are added to steel,
There is a method of adding r to lower the alloy and increasing the corrosion resistance of the reinforcing bar itself. However, the anticorrosion effect as expected is not obtained, and it is not used much.

[0007] More recently, a method of shielding the concrete itself from a corrosive environment by applying heavy corrosion protection to the surface of the concrete has begun to be studied, but the disadvantage of increasing the cost is inevitable.

[0008] Further, corrosion of steel buried in the soil, such as buried pipes in the soil or foundation steel structures in the soil of a building, may cause rainwater to penetrate to the surface of the steel when the groundwater level is relatively low. It progresses due to the action of the water that has escaped and the oxygen that diffuses from the surface.

In the case where such corrosion of the steel material in the soil becomes a problem, measures such as galvanization and heavy corrosion protection lining have been taken as a method of preventing corrosion.

[0010] However, heavy corrosion protection linings, although capable of complete corrosion protection, increase costs and are rarely used except for gas pipes from the viewpoint of economy. The anticorrosion method using galvanizing also has a problem that corrosion is unavoidable in the long term, depending on the basis weight of plating, and is inexpensive and effective for steel structures used in soil. The development of an effective anticorrosion method was desired.

[0011] Further, in an environment where a large amount of salt flies, such as a coastal zone or an area where a deicing agent such as rock salt is sprayed, conventionally, a steel having a high Cr content and a high Mo content higher than SUS304 stainless steel having excellent corrosion resistance is used. Have been used. A chromium steel having a Cr content lower than this class, for example, having a Cr content of about 13% or less, is not used in a place having a large amount of flying salt because red rust is generated and pitting corrosion proceeds considerably deeply. .

[0012] However, even in the case of stainless steel, rust often occurs depending on the use conditions, and there is a strong demand for the development of a steel material having excellent corrosion resistance that can be used in places with a high amount of flying salt such as coastal areas. .

[0013]

SUMMARY OF THE INVENTION In view of such circumstances, the present invention has been developed mainly for use in steel materials mainly used in civil engineering and building structures, especially in coastal areas and areas where antifreezing agents such as rock salt are sprayed. An object of the present invention is to provide a method for treating a corrosion-resistant surface of steel used in an environment in which chlorides fly, a treated steel having a corrosion-resistant surface treated with the method, and a method of using the same.

More specifically, the steel material subjected to the anticorrosion surface treatment is used as a steel material used in concrete (hereinafter, also referred to as "steel material for concrete") such as a reinforcing steel or a steel frame of a concrete structure, or as a soil. A method of using as a steel material for a steel structure buried therein (steel material for a structure buried in the soil), and a Cr steel (here, Cr
It is an object of the present invention to provide an anticorrosion surface treatment method that can be used without causing pitting corrosion even in a place with a large amount of incoming salt such as a coastal zone.

[0015]

Means for Solving the Problems As a result of repeated studies to solve the above-mentioned problems, the present inventors have found that a fine rust layer having a protective property on the surface of a steel material (from fine chromium-substituted goethite). It was confirmed that the method of forming a rust layer was effective.

That is, SO ₄ ^2- and Cr ³⁺ are formed on the surface of a steel material.
While the resin film formed by applying the specific resin paint containing the compound suppresses the penetration of anions (Cl ⁻ ) into the surface of the steel material, oxygen (O ₂ ) and water (H the ₂ O) and the steel surface α- (Fe _1-x, Cr
_x ) A dense rust layer (hereinafter referred to as "stable rust layer") made of OOH (chromium-substituted goethite) is formed. Resin film is deteriorated by oxidation or the like over time, stable rust layer is Cl ^- because it has a function of suppressing the penetration, it is possible to effectively suppress the progress of subsequent corrosion.

This stable rust layer is also formed on the surface of a steel material such as a reinforcing bar or a steel frame used in concrete. Moisture (H ₂ O) and oxygen (O ₂ ) that diffuse into and penetrate the concrete reach the surface of steel such as a reinforcing bar, where a stable rust layer is formed. This rust layer is formed of α- (FeOOH (goethite) in which a part of Fe is replaced by Cr.
_1-x , Cr _x ) A dense rust layer made of OOH (chromium-substituted goethite).

On the other hand, the corrosion of steel in the soil is caused by the fact that, when the groundwater level is relatively low, the rainwater seeps into the soil and reaches the surface of the steel material (H ₂ O) and the surface of the steel surface is corroded. It progresses by the action of oxygen (O ₂ ) diffused from
It is phenomenally similar to atmospheric corrosion, and likewise in the case of atmospheric corrosion, α- (Fe _1-x , Cr _x )
A dense stable rust layer made of OOH (chromium-substituted goethite) is formed.

Further, by applying the above resin paint to the surface of chromium steel, α- (Fe _1-x , C
It was confirmed that a dense and stable rust layer composed of (r _x ) OOH (chromium-substituted goethite) could be formed, and that this rust layer effectively suppressed pitting corrosion and subsequent growth of chromium steel. .

Further, PO ₄ ^3- , MoO _{4
^{2-, WO 4 2-, VO 3}} - and NO ₃ ^- in the oxyacid allowed to contain any one or more of (oxo acid) ions, inhibition of corrosion (pitting in the case of chromium steel) Was found to be effective.

The gist of the present invention resides in the following methods (1) to (3) of using a corrosion-resistant surface-treated steel material, (4) using a corrosion-resistant surface-treated steel material, and (5) using a corrosion-resistant surface-treated steel material.

(1) On the surface of steel material, 0.1 to 15% by mass of chromium sulfate with respect to the solid content of the resin coating, butyral resin, or a mixture of butyral resin and a resin compatible with butyral resin. An anticorrosion surface treatment method for a steel material, comprising applying a resin paint containing 10 to 40% by mass of a resin as a main component.

(2) The resin paint further comprises PO ₄ ³⁻ , M
^{_{oO 4 2-, WO 4 2-,}} VO 3 - and NO ₃ ^- (3) above, characterized in that it contains one or more one of the oxygen acid ions of the steel is a Cr 1 to 13 wt% The anticorrosion surface treatment method for a steel material according to any one of the above (1) and (2), which is a chromium steel contained.

(4) The surface of the steel material has a chromium sulfate concentration of 0.1 to 0.1.
A resin film containing, as a main component, 15% by mass and 10 to 40% by mass of a butyral resin or a mixture of a butyral resin and a resin compatible with the butyral resin, or PO ₄ ³⁻ and MoO ₄ ^{2 -} , WO ₄ ^2- ,
VO ₃ ^- and NO ₃ ^- one of the oxygen acid ions of 1
A corrosion-resistant surface-treated steel material characterized by being coated with a resin film containing at least one species.

(5) A steel material which has been subjected to anticorrosion treatment by the method according to any one of (1) and (2) above, and is used for concrete or a structure buried in soil. how to use.

The “solid content of the resin coating” is defined as resin,
Refers to chromium sulfate, oxyacid ions such as PO ₄ ³⁻ and MoO ₄ ²⁻ , and paint additives such as pigments added to resin paints. Evaporates by natural drying after application, such as solvents added when preparing resin paints. In addition, those that do not remain in the resin film formed on the surface of the steel material (hereinafter, also simply referred to as “film”) are not included. That is, it refers to a “resin coating”. However, when the above-mentioned oxyacid ion is added as, for example, a Na salt or a K salt, Na ⁺ and K ⁺ remain in the coating, but these cations are not included here.

The term "chromium steel" is a name representing a material, but here also represents a steel material of that material.
The chromium steel referred to in this specification has a Cr content of 1 to 1.
13% by mass of steel.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for treating a steel material according to the present invention (inventions of (1) to (3) above), a (4) corrosion-resistant surface-treated steel material and (5) a corrosion-resistant surface-treated steel material How to use will be described in detail. In addition, "%" of resin, chromium sulfate and oxyacid ions and "%" of chromium steel mean "% by mass".

You can to some extent prevent the penetration into the steel surface of the - ^(Cl) [0029] (i) chloride ions by the coating so long as the resin film to be formed on the surface of the chromium sulphate steel is healthy. Resin coating is degraded with the passage of time, during which, through the resin film reaches the surface of the steel product oxygen (O ₂₎ and water (H ₂ O) on the steel surface by the action of α- (Fe _1-x, If a dense stable rust layer made of Cr _x ) OOH (chromium-substituted goethite) can be formed, even if Cl ⁻ subsequently penetrates the coating, the stable rust layer prevents the steel from reaching the surface of the steel material, and prevents corrosion. Or the occurrence of pitting and subsequent growth can be suppressed. For that purpose, it is necessary to form a dense and defect-free continuous stable rust layer (chromium-substituted goethite) on the surface of the steel material.

Chromium sulfate in the resin film formed on the surface of the steel material causes SO ₄ ²⁻ and C ₄
Dissociates into r ³⁺ and reaches the interface between the coating and steel. Where S
O ₄ ^2-is involved in the reaction between the steel and the O ₂ in the presence of H ₂ O,
Most of the generated rust is converted to α-FeOOH (goethite).

On the other hand, Cr ^{3+ not} only accelerates the above reaction, but also replaces part of Fe with Cr to form fine α-
(Fe _1-x , Cr _x ) OOH (chromium-substituted goethite)
Plays the role of generating. The chromium-substituted goethite contains an anion (Cl ^- etc.) by containing Cr.
To have cation selectivity to selectively permeate cations from anion selectivity to selectively permeate,
Cl ^- in so prevents penetration of the stable rust layer, except if such direct contact with the sea water, corrosion resistance is significantly better.

As described above, chromium sulfate is closely involved in the formation of chromium-substituted goethite constituting the stable rust layer.

In order to form a stable rust layer on the surface of the steel material into which Cl ^- has penetrated through the coating, it is necessary to contain 0.1% or more chromium sulfate in the resin coating. However, when the content exceeds 15%, the number of defects in the coating increases, and the deterioration of the coating is accelerated. Therefore, the content of chromium sulfate is set to 0.1 to 15%.

The formed stable rust layer (chromium-substituted goethite) has a selectivity from an anion selectivity to a cation selectivity by containing Cr, and prevents the penetration of Cl ^-into the stable rust layer. Pitting for chrome steel)
Is unlikely to occur.

Further, in some Cl ^- mainly goethite because even occurs reached corrosion or pitting to steel surfaces, there is SO ₄ ^2-stable rust layer (alpha-FeOOH)
^Are generated, and at the same time, the presence of Cr ³⁺ results in fine chromium-substituted goethite, covering the corroded or pitted portions, and the growth of corrosion or pits is suppressed.

Further, in the case of chrome steel, Cr in steel
Is contained in the corrosion product as Cr ³⁺ , the rust generated in the pit portion has a high Cr content, and the corrosion resistance increases accordingly. As described above, even if pitting occurs, the pitting does not proceed, and pitting occurs newly in other portions. As this process is repeated, the entire surface of the chrome steel is red-rusted, but no pitting occurs.

Cr ³⁺ and SO were separately used without using chromium sulfate.
₄ ^2- , for example, Cr (NO ₃ ) ₃ and Na ₂ SO
₄ may be contained in the resin paint. However, the use of chromium sulphate has the advantage that only one chemical needs to be added. It is to be noted that chlorides such as CrCl ₃ promote corrosion and hinder stabilization of rust, and thus are not preferred.
However, there is no problem if a small amount (5% or less) is added to the sulfate (Na ₂ SO ₄ ) added at the same time.

(Ii) Resin The resin as the binder used in the method of the present invention is a resin comprising butyral resin alone or a mixture of butyral resin and a resin compatible with butyral resin (for example, melamine resin or phenol resin). is there. Butyral resin is an indispensable component in the resin coating used in this method, since it is very flexible and can easily follow the change of the steel material surface due to the formation of the rust layer.

If the amount of the resin as the binder is less than 10% based on the solid content of the resin coating, a uniform coating cannot be obtained when the resin coating is applied to the surface of the steel material. And low adhesion. On the other hand, if it exceeds 40%, the amount of water that permeates through the coating decreases,
The formation of a stable rust layer is significantly delayed. Therefore, the resin amount was set to 10 to 40%.

In the above-mentioned coating film, the resin has an active anticorrosion function as described below in addition to the function as a binder. That is, the resin film is originally a cation selective, plays the role of preventing the permeation of chlorine to the steel surface until the coating is deteriorated, Cl therebetween ^- to form a transparent hard stable rust Because you get it.

(Iii) Formation of Coating A predetermined amount of chromium sulfate is added to the above resin, and an appropriate amount of a solvent or water is added to obtain a resin coating having a viscosity suitable for the coating operation. Coloring pigments such as iron, titanium dioxide, carbon black, and phthalocyanine blue;
Extender pigments such as talc, silica, mica, barium sulfate, calcium carbonate, etc., rust preventive pigments such as chromium oxide, zinc chromate, lead chromate, basic lead sulfate, and other thickeners, dispersants, reaction accelerators, etc. Additives may be added.

Further, phosphoric acid or an aqueous solution thereof may be added. Rather, the coexistence of phosphoric acid and chromium ions promotes the formation of chromium-substituted goethite.
That is preferred.

The resin paint obtained as described above is applied to the surface of the steel material by a conventional method such as air spray, airless spray or brushing in the same manner as the usual paint application. The solvent or moisture evaporates by air drying after application.

The steel material is not limited to the weather-resistant steel, but may be any other steel that generates so-called rust, such as other low alloy steels and ordinary steels. It may be a chromium steel containing 1 to 13% of Cr.

It is desirable that the film thickness at the time of application be 5 to 50 μm after the resin coating is dried and solidified. With this thickness, the balance between the supply of chromium ions and iron ions to the steel surface at the stage of forming the stable rust layer is optimal.

Since the application can be performed anywhere, irrespective of the place, the method is applied not only to the case where it is carried out before shipment by the manufacturer, but also to the case where the steel material is cut at the construction site and subjected to processing such as welding. be able to. In addition, since the effect can be obtained by one coating, the cost is also excellent. In addition, when applying to a reinforcing bar, a steel frame, or the like used for a concrete structure, it is possible before the concrete is cast.

The surface of the steel material before coating may be polished, pickled, shot blasted, etc.
Any of them may be used. This method can be applied even when rust is generated on the surface.

The above-described method of applying a resin paint containing chromium sulfate and a resin as main components to the surface of a steel material is the method for treating a steel material according to the invention (1).

According to this method, it is possible to form a dense and stable rust layer on the surface of a steel material even in a harsh environment where chlorides fly, such as a coastal zone, and suppress the progress of subsequent corrosion or pitting corrosion. it can.

In the method of the invention of (1), even if some external force acts on the stable rust layer to cause cracking or peeling of the rust layer, if chromium sulfate remains in the coating of the healthy part, Chromium sulfate is supplied from the healthy part to the damaged part, and the self-repairing performance of generating a stable rust layer again can be expected.

The invention of the above (2) is characterized in that the resin paint used in the method of the invention of (1) further comprises PO ₄ ³⁻ , MoO ₄ ²⁻ ,
WO ₄ ^2-, VO ₃ ^- is a corrosion surface treatment of steel using a resin coating material that contains one or more one of the oxygen acid ions ^- and NO _3.

[0052] To explain the [oxygen acid ions] Specific examples include, for example corrosion by chloride steel in concrete, Cl which has penetrated into the concrete ^- begins by local destruction of the passive film of by the steel surface In this case, PO ₄ ^3- , MoO ₄ ^2- , WO ₄ ^2- , VO ₃ ^- or N
O ₃ ^- the oxygen acid ions are present in the rust, the destruction of the passive film is suppressed. In addition, the above-mentioned oxyacid ion may be one kind, or may be any two or more kinds.

The effect of inhibiting the corrosion of oxyacid ions is remarkably recognized when the content of oxyacid ions in the resin coating is 0.01% or more in total with respect to the solid content of the resin coating. Can be On the other hand, if the content exceeds 10%, the number of defects in the coating increases, and the protective property is impaired. Therefore, the content of oxyacid ions is 0.01 to 1 in total.
It is desirable to set it to 0%.

It is to be noted that Cl that has penetrated into the concrete
^{When the} amount is large, the passivation film is destroyed even in the presence of oxyacid ions, but in the presence of SO ₄ ²⁻ , α-FeOOH (goethite) is mainly generated, and Cr ³⁺
Is a fine chrome-substituted goethite,
The pits are covered, and the progress of corrosion thereafter is suppressed.

The biggest problem with chloride corrosion in soil is pitting corrosion caused by macrocells. Even in the pit portion, which is the anode, the rust formed is mostly composed of chromium-substituted goethite by the action of chromium sulfate, and has a protective property.
_{^{O 4 3-, MoO 4 2-,}} WO 4 2-, VO 3 - the oxygen acid ions are present, Cl ^{- -} or NO ₃ becomes barrier to, Cl to the steel surface ^- since the transmission is suppressed, The progress of corrosion is also suppressed. In addition, the above-mentioned oxyacid ion may be one kind, or may be any two or more kinds.

Such an effect of inhibiting the corrosion of oxyacid ions is remarkably observed when the resin coating material contains 0.01% or more of oxyacid ions in total as in the case of the above-mentioned steel material for concrete. On the other hand, if the content exceeds 10%, the number of defects in the coating increases, and the protective property is impaired. Therefore, the content of oxyacid ions is 0.01 to
It is desirable to set it to 10%.

In chromium steel, corrosion exhibits a pitting state, and is observed as a phenomenon of multiple occurrences of pitting. However, as described above, even if pitting occurs by applying a resin paint containing chromium sulfate to the surface of chrome steel,
₄ ^2- and fine chromium substituted goethite produced by the action of the Cr ³⁺ covers the pitting unit, the progress of pitting corrosion can be suppressed. At this time, PO ₄ ^3- , MoO
^{_{4 2-, WO 4 2-, VO}} 3 - or NO ₃ ^- When contains oxygen acid ions, these ions act as inhibitors of pitting, pitting, is relieved to grow both. The oxyacid ion may be one kind,
There may be more than one species.

Such an effect of inhibiting the corrosion of oxyacid ions against pitting corrosion of chromium steel is recognized when the resin coating material contains 0.01% or more of oxygen acid ions in total. On the other hand, if the content exceeds 10%, the number of defects in the coating increases, and the protective property is impaired. Therefore, the total content of oxyacid ions is desirably 0.01 to 10%.

In the method (2) of the invention, the oxyacid ion may be contained in the resin by adding it as a Na salt, a K salt or the like. When adding PO ₄ ^3-, if less than 1% of small amounts, it may be added in H ₃ PO _4.

It is needless to say that SO ₄ ^2- is also an oxyacid ion, and has an effect of suppressing Cl ⁻ penetration into the stable rust layer similarly to the above-mentioned oxyacid ion.

According to the method (2) of the invention, first,
Cl in the resin film of the steel material surface ^- penetration is suppressed to some extent, Cl come permeates through the film ^- its aggressiveness are weakened by the oxygen acid ions. In addition, most of the generated rust layer is fine chromium-substituted goethite, and the corrosion after the resin film has deteriorated is suppressed by this rust layer, but the rust layer contains oxygen acid ions. cation selectivity of the rust layer is strengthened further, Cl ^-
Is weakened. Therefore, Cl ^- corrosion or pitting is less likely to occur by.

The method of the present invention according to (3) is a method according to (1) or (2), wherein the steel material contains 1 to 13 Cr.
%, A stable rust layer can be formed as described above.

As described above, the chromium steel having a Cr content of 1 to 13% is not intended for high-Cr, high-Mo steels such as SUS304 stainless steel having excellent corrosion resistance, but for lower-grade materials. This is because it is assumed that this is subjected to a surface treatment and used without causing pitting corrosion.

Since a stable rust layer is formed on the surface of this chromium steel, it can be used without causing pitting corrosion even in a place where a large amount of salt comes in, such as a coastal zone which has been conventionally unsuitable. Thus, it is possible to provide a less expensive material.

The corrosion-resistant surface-treated steel material of the invention (4) is as follows:
The steel material subjected to the rust stabilization treatment by the method of the above-mentioned (1) or (2), that is, a resin whose surface is compatible with a predetermined amount of chromium sulfate and butyral resin, or butyral resin and butyral resin Or a resin film containing as a main component a resin consisting of a mixture of PO ₄ ³⁻ , MoO ₄ ²⁻ , WO ₄ ²⁻ , VO ₃ ⁻ and NO ₃ ^−.
Is a steel material coated with a resin film containing at least one of the above oxyacid ions.

As described above, the material steel is not limited to the weather-resistant steel, but may be other low-alloy steel, ordinary steel, or other steel that generates so-called rust. Cr 1 to
It may be a chromium steel containing 13%.

The shape of the raw steel is not limited at all.
As described above, it may be a steel material after performing processing such as cutting and welding, a polished state, a state after being pickled,
A state in which shot blasting has been performed or a state in which rust has occurred on the surface may be employed.

A resin, and chromium sulfate added to the resin;
The functions and effects of the oxyacid ions and the reasons for limiting their contents are as described above.

The thickness of the resin film is 5 to 5 as described above.
It is preferably 0 μm.

The method according to the invention (5) is characterized in that the steel material subjected to the anticorrosion surface treatment by the method according to the invention (1) or (2), that is, the steel material subjected to the anticorrosion surface treatment according to the invention (4) is used as a steel material for concrete or This method is used as steel for underground structures.

[0071] As described above, even when the concrete structure is constructed in a large amount of location chloride is flying, such as coastal areas, or from the first soil Cl ^- contained in the corrosive ions large amount of such Even if it is, a stable rust layer can be formed. Therefore, the concrete structure even when a large amount of chloride, such as coastal areas is built in place of flying, or Cl from the first soil ^- be sufficiently used even when the corrosive ions such as contained in a large amount can do.

[0072]

【Example】

(Example 1) A round bar having the composition shown in Table 1 was used as a test material.
Each of the test pieces (diameter 10 mm × length 100 mm) to which the resin paint shown in (1) was applied was poured into concrete as shown in FIG. 1 to prepare a concrete block specimen. Table 3 shows the composition of the concrete used.
The test material (round bar) was used after removing the mill scale on the surface with sulfuric acid in advance so that the corrosion weight loss could be easily obtained.

Resin paints are, in addition to the resins, chromium sulfate and oxyacid ions shown in Table 2, as pigments,
Silica, barium sulfate or the like is added as appropriate, and a solvent (thinner) is added to obtain a viscosity (measured by a B-type viscometer) of 200 to 100.
It was adjusted to be 0 centipoise (cps). This resin coating material was applied to the surface of a test material having the above dimensions so as to have a predetermined film thickness shown in Table 2 by air spray to prepare a test piece.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

The above concrete block specimen was
Using artificial seawater at 0 ° C., [wet: 6h → dry: 6
h] as one cycle was performed for three months.

The test results are shown in Table 2.

In this table, “average corrosion amount” means the corrosion depth per year from the weight difference between before and after the test after removing the coating and rust on the surface of the test piece taken out of the concrete. It is what I sought. Also,
"Presence or absence of chromium-substituted goethite" was confirmed by performing elemental analysis of rust and identifying rust by Raman spectroscopy of a cross section of the rust layer. Further, the existence of a stable rust layer was checked by observing the cross section of the rust layer with a polarizing microscope (the stable rust layer was quenched). The numbers in the column of “Material of test material” are No. (Ie, material).

From the results shown in Table 2, the examples of the present invention (No.
In each of 1) to 12), a stable rust layer composed of chromium-substituted goethite was formed, and the average corrosion amount was 0.01 mm / y.
In contrast, in Comparative Examples (Nos. 13 to 17), no stable rust layer was formed, and the amount of corrosion was large.

In the examples of the present invention, when oxyacid ions were added to the resin coating, no oxyacid ions were added (No.
1, 5, 8 and 10), the amount of corrosion was small, and the effect of adding oxygen acid ions was observed.

Although not shown, SiO ₃ ^2- , B
The same effect was observed when a resin paint to which other oxygen acid ions such as O ₃ ⁻ and CO ₃ ^2- was added was applied to the surface of the test material.

(Example 2) Using a steel having a composition shown in Table 4 as a test material, a test piece coated with a resin paint shown in Table 5 was prepared and subjected to a soil burial corrosion test, and the corrosion amount after the test was determined. It was measured.

The dimensions of the test piece were 50 mm × 300 mm ×
5 mm (thickness).

For the resin coating, bengara, silica, barium sulfate and the like are appropriately added as pigments in addition to the resin, chromium sulfate and oxyacid ions shown in Table 5, and a solvent (thinner)
To add a viscosity of 200 to 1000 centipoise (cp
s). This resin coating material was applied to the surface of a test material having the above dimensions so as to have a predetermined film thickness shown in Table 2 by air spray to prepare a test piece.

The soil burial corrosion test was carried out by burying the test piece after applying the paint horizontally in a 50 cm deep soil for 4 years. Incidentally, will accelerate corrosion, Cl to corrosion ^- assuming also the action of the beginning of the test, the artificial rain (3% NaCl aqueous solution) was 5 mm (rainfall) spraying.

[0087]

[Table 4]

[0088]

[Table 5]

The test results are shown in Table 5.

In this table, the “average corrosion amount” in the column of “corrosion amount” is obtained by removing the film and rust on the surface of the test piece after the test, measuring the weight, and calculating the weight difference per year from the weight difference before and after the test. The maximum corrosion depth was measured using a point micrometer. "Presence or absence of chromium-substituted goethite" was confirmed by performing elemental analysis of the rust and identifying the rust by Raman spectroscopy of the cross section of the rust layer. Further, the presence of a stable rust layer was checked by observing the cross section of the rust layer with a polarizing microscope.

From the results shown in Table 5, the examples of the present invention (No.
In any of 1 to 10), a stable rust layer composed of chromium-substituted goethite was formed, and the average corrosion amount was 0.01 mm / y.
However, in Comparative Examples (Nos. 11 to 15), no stable rust layer was formed, and both the average corrosion amount and the maximum corrosion depth were larger than those of the present invention.

In the examples of the present invention, when oxyacid ions were added to the resin coating, no oxyacid ions were added (No. 1).
Both of the average corrosion amount and the maximum corrosion depth were smaller than those of (10) and (10), and the effect of oxygen acid ion addition was recognized.

Although not shown, SiO ₃ ^2- , B
The same effect was observed when a resin paint to which other oxygen acid ions such as O ₃ ⁻ and CO ₃ ^2- was added was applied to the surface of the test material.

(Example 3) Using a steel having a composition shown in Table 6 as a test material, a test piece coated with a resin paint shown in Table 7 was prepared, and the specimen was prepared in a coastal zone (a place 100 m away from the coast (Naoetsu, Niigata Prefecture). 2) Atmospheric exposure test was conducted for 2 years, and the maximum pit depth after the test was measured.

The dimensions of the test piece were 60 mm × 100 mm ×
3 mm (thickness).

[0096] In addition to the resins, chromium sulfate and oxyacid ions shown in Table 7, pigments such as red iron oxide, silica, barium sulfate and the like are appropriately added to the resin coating material,
To add a viscosity of 200 to 1000 centipoise (cp
s). This resin paint was applied to the surface of a test material having the above dimensions so as to have a predetermined film thickness shown in Table 7 by air spray to obtain a test piece. The surfaces of the test materials were all polished with emery paper (No. 600).

[0097]

[Table 6]

[0098]

[Table 7]

The test results are shown in Table 7.

In this table, the "maximum pit depth" was measured using a point micrometer. "Presence or absence of chromium-substituted goethite" was confirmed by performing elemental analysis of the rust and identifying the rust by Raman spectroscopy of the cross section of the rust layer. Further, the presence of a stable rust layer was checked by observing the cross section of the rust layer with a polarizing microscope. The numbers in the column of “Material of test material” correspond to No. in Table 6. (Ie, material).

From the results shown in Table 7, the examples of the present invention (No.
In each of Examples 1 to 14), a stable rust layer composed of chromium-substituted goethite was formed, and the maximum pit depth was as shallow as 7 μm or less. However, in Comparative Examples (Nos. 15 to 19), a stable rust layer was formed. However, the maximum pit depth was as deep as 20 μm or more.

Further, in the examples of the present invention, when oxyacid ions were added to the resin coating, no oxyacid ions were added (No.
1, 2, 9 and 11) the maximum pit depth is shallower than
The effect of adding oxyacid ions was observed.

Although not shown, SiO ₃ ^2- , B
The same effect was observed when a resin paint to which other oxygen acid ions such as O ₃ ⁻ and CO ₃ ^2- was added was applied to the surface of the test material.

[0104]

According to the anticorrosion surface treatment method for steel materials of the present invention, the surface of steel materials can be densely packed even in an environment where chlorides fly, such as in coastal areas or areas where antifreezing agents such as rock salt are sprayed. A stable rust layer can be formed to suppress the progress of corrosion. Therefore, the anticorrosion surface-treated steel material of the present invention which has been subjected to this treatment can be used as a relatively inexpensive steel material for civil engineering, building structures and the like even under such a severe environment.

For example, as a steel material for concrete such as a reinforcing steel bar or a steel frame of a concrete structure, or as a steel material for a submerged underground structure used in soil such as a submerged piping or a foundation steel structure underground in a building. It is possible to provide chromium steel that can be used without causing pitting even in places with a large amount of salt coming in as an inexpensive alternative to high Cr high Mo steel etc., which has excellent corrosion resistance. Becomes

[Brief description of the drawings]

FIG. 1 is an explanatory view of a method of manufacturing a concrete block specimen used in an example, (a) is a longitudinal sectional view of the specimen,
(B) is a sectional view taken along the line AA of (a).

Claims (5)

[Claims] 1. A resin comprising, on the surface of a steel material, 0.1 to 15% by mass of chromium sulfate with respect to the solid content of a resin coating, butyral resin, or a mixture of butyral resin and a resin compatible with butyral resin. An anticorrosion surface treatment method for a steel material, comprising applying a resin paint containing 10 to 40% by mass as a main component. 2. The resin paint further comprises PO ₄ ³⁻ , MoO _{4
^{2-, WO 4 2-, VO 3}} - and NO ₃ ^- anticorrosion surface treatment of steel product according to claim 1, characterized in that it contains one or more one of the oxygen acid ions. 3. The method according to claim 1, wherein the steel is a chromium steel containing 1 to 13% by mass of Cr. 4. A steel material comprising, as a main component, 0.1 to 15% by mass of chromium sulfate and 10 to 40% by mass of a resin comprising butyral resin or a mixture of butyral resin and a resin compatible with butyral resin. resin coating containing or additionally ^{_{PO 4 3-, MoO 4 2-,}} WO 4 2-, VO 3 -
A corrosion-resistant surface-treated steel material characterized by being coated with a resin film containing at least one of oxygen and NO ₃ ⁻ oxyacid ions. 5. A method of using a corrosion-resistant surface-treated steel material, wherein the steel material subjected to the corrosion-resistant surface treatment according to claim 1 is used for concrete or for a structure buried in soil.